In one-time programmable (OTP) memory, which is a form of digital memory, the setting of memory bits may be locked by using a fuse or an anti-fuse for each bit. Most OTP memories may require a programmable fuse element along with a select device (e.g., a switch), implementation of which can limit the cell density and may often increase process integration complexity. Many select devices are realized using thick oxide layers, which can limit scaling from one technology node to the next. For example, some of the existing OTP memory architectures may not be extendable to the advanced FinFet technology node.
Existing OTP memories use transistor anti-fuses that after programming may ideally form a diode-connected transistor where the gate is shorted to the channel through a point of rupture in the oxide layer that can act as a drain terminal. The anti-fuse cells may be realized by using thin or split-oxide layers. The thin-oxide anti-fuse cells typically need a select device for proper operation, therefore, cannot be used in cross-point diode array configurations, as it can form an ohmic contact directly to the source instead of forming a diode connected transistor. Split-oxide anti-fuse cells may be used in cross-point diode array configurations without a select device, but the cell structure may not be extendable to FinFet technology node. The split-oxide anti-fuse cells require the mix of thin and thick oxide devices in a single cell, which can reduce cell density, complicate process integration, and may not be applicable to advanced technology nodes such as FinFet.